Combined long rail/short rail IVUS catheter

A catheter is provided that allows a user to operate the catheter in either long rail or monorail mode. The catheter comprises a distal region with two distal tips and a proximal region which defines a common lumen configured to receive a working element. The distal region comprises a long rail aperture that is configured to receive a guidewire and that is communication with a long rail distal tip. The distal region of the catheter further comprises a short rail aperture that is configured to receive a guidewire and that is in communication with a short rail distal tip. In operation, a proximal end of the guidewire may be selectively inserted into either the long rail distal tip or the short rail distal tip.